This project is designed to investigate neurogenic activity in the somatosensory regions of the cerebral cortex that is elicited by respiratory sensory systems. There is very little known about respiratory afferent activation of cortical neurons or the pathways to the cortex. Yet, it is intuitively sensible that respiratory afferents activate somatosensory regions of the cortex by the "common knowledge" that humans can sense and voluntarily control their breathing. It is, in fact, surprising that so little investigation of respiratory afferent activation of the cortex has been made. This project will not attempt to investigate all respiratory afferent input to the cerebral cortex, rather it will concentrate on respiratory muscle afferent projections that have been previously studied by these investigators. The general objectives of this project are to investigate the higher brain center processing of respiratory muscle afferent information. The specific goals are to determine the input coding of respiratory muscle mechanoreceptors using controlled intercostal muscle stretching as a model. The central processing of both this intercostal muscle and phrenic afferent information will be initially investigated in the sensorimotor cortex. The organization of the sites of respiratory muscle activation in this region will be studied functionally and anatomically. Potential afferent and efferent connections will be identified with neuronal labeling and thereby provide clues for the functional identification of the subcortical input pathways for respiratory muscle afferents. The thalamus, a highly probable relay site, will be studied and the thalamocortical connections of respiratory muscle afferent activated neurons determined. These functional and anatomical studies lay the foundation for future studies on the, as yet unknown subthalamic projection pathways for respiratory muscle afferents. Determination of the projection and processing of respiratory muscle afferents by higher brain centers provides a basis for continued study of the mechanism of respiratory sensation.